[AIRFLOW-5688] Merge alembic migrations

[Fokko]

We have two heads in the migrations:

$ alembic branches
939bb1e647c8 (branchpoint)
             -> 6e96a59344a4
             -> 004c1210f153 (head)

c8ffec048a3b (branchpoint)
             -> dd4ecb8fbee3
             -> a56c9515abdc

41f5f12752f8 (branchpoint)
             -> c8ffec048a3b (branchpoint)
             -> cf5dc11e79ad

9635ae0956e7 (branchpoint)
             -> dd25f486b8ea
             -> 0a2a5b66e19d

d2ae31099d61 (branchpoint)
             -> 33ae817a1ff4
             -> 0e2a74e0fc9f

$ alembic heads
004c1210f153 (head)
74effc47d867 (head)

Make sure you have checked all steps below.

Jira

• My PR addresses the following Airflow Jira issues and references them in the PR title. For example, "[AIRFLOW-XXX] My Airflow PR"
  • https://issues.apache.org/jira/browse/AIRFLOW-XXX
  • In case you are fixing a typo in the documentation you can prepend your commit with [AIRFLOW-XXX], code changes always need a Jira issue.
  • In case you are proposing a fundamental code change, you need to create an Airflow Improvement Proposal (AIP).
  • In case you are adding a dependency, check if the license complies with the ASF 3rd Party License Policy.

Description

• Here are some details about my PR, including screenshots of any UI changes:

Tests

• My PR adds the following unit tests OR does not need testing for this extremely good reason:

Commits

• My commits all reference Jira issues in their subject lines, and I have squashed multiple commits if they address the same issue. In addition, my commits follow the guidelines from "How to write a good git commit message":
  1. Subject is separated from body by a blank line
  2. Subject is limited to 50 characters (not including Jira issue reference)
  3. Subject does not end with a period
  4. Subject uses the imperative mood ("add", not "adding")
  5. Body wraps at 72 characters
  6. Body explains "what" and "why", not "how"

Documentation

• In case of new functionality, my PR adds documentation that describes how to use it.
  • All the public functions and the classes in the PR contain docstrings that explain what it does
  • If you implement backwards incompatible changes, please leave a note in the Updating.md so we can assign it to a appropriate release

[ashb]

I thought I updated the template used to generate the migrations in #6216 but I obviously missed this case :(

Fancy updating the config like https://alembic.sqlalchemy.org/en/latest/autogenerate.html#basic-formatter-configuration using black or zimports in another PR?

[codecov-io]

Codecov Report

Merging #6362 into master will increase coverage by 0.27%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #6362      +/-   ##
==========================================
+ Coverage   79.82%   80.09%   +0.27%     
==========================================
  Files         616      616              
  Lines       35794    35795       +1     
==========================================
+ Hits        28572    28670      +98     
+ Misses       7222     7125      -97

Impacted Files	Coverage Δ
airflow/contrib/hooks/ssh_hook.py	88.49% <0%> (+0.1%)	⬆️
airflow/models/taskinstance.py	93.79% <0%> (+0.5%)	⬆️
airflow/hooks/dbapi_hook.py	88.13% <0%> (+0.84%)	⬆️
airflow/models/connection.py	65% <0%> (+1.11%)	⬆️
airflow/jobs/backfill_job.py	91.43% <0%> (+1.52%)	⬆️
airflow/hooks/hive_hooks.py	77.6% <0%> (+1.78%)	⬆️
airflow/jobs/local_task_job.py	90% <0%> (+5%)	⬆️
airflow/utils/sqlalchemy.py	93.22% <0%> (+6.77%)	⬆️
airflow/operators/mysql_operator.py	100% <0%> (+100%)	⬆️
airflow/operators/mysql_to_hive.py	100% <0%> (+100%)	⬆️

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